A variety of methods have been used in the past to position and locate reinforcing rods within concrete structures. It is well known in the construction trade that concrete structures and hollow block walls must be reinforced to improve structural integrity. Such reinforcement is often accomplished by introducing metal bars or rods commonly known as reinforcing rods, reinforcing bars, or simply "rebars" throughout the structure. Typically, these rods are comprised of construction grade steel alloy. The present invention relates generally to steel reinforcement used in concrete block construction, and more particularly to a device for locating and positioning vertical steel reinforcing rods in appropriate locations during construction of a block wall. Further, the present invention is intended to precisely position the reinforcing rod so that the full tensile strength of the rod may be realized, thus meeting specified building codes and designs.
A common method for building walls is through the use of hollow blocks, also known as concrete masonry units (C.M.U.'s). These C.M.U.'s are also referred to as "cinder" or "concrete" blocks. These blocks are generally rectangular in shape and have two hollow cavities or cells located adjacent one another which extend through the central portion of the block. The cells are separated by a central web portion. In the construction of a wall, the blocks are laid in end to end horizontal alignment and joined using a cementitious binder, usually a mortar. Successive courses of blocks are then provided on top of the initial course. These successive courses are positioned so that the individual cells of each block partially align with the hollow cells of the blocks located in the courses below. Blocks are typically arranged in a staggered arrangement, known as a half-lap joint. In this form of construction, blocks are positioned to overlap those blocks immediately below to form a more stable wall structure. This arrangement results in the formation of a plurality of hollow cores extending vertically through the wall.
Masonry structures comprised of hollow blocks must often be reinforced to comply with design specifications and building codes. Reinforcement may be accomplished using several techniques. One of the most common techniques is through the installation of vertical reinforcing rods in the hollow cores of the wall. As stated above, the hollow cells of the individual blocks are aligned with the hollow cells of the blocks directly above and below to form hollow cores which extend vertically through the height of the wall. To strengthen the wall, cement, grout, mortar or some other form of cementitious binder is poured, pumped or injected into the cores after the vertical rods are installed. The cores are typically filled with grout, a thin form of mortar, which surrounds the rods and later hardens, to increase the strength of the wall.
In construction practice, reinforcing bars are generally provided in six foot lengths. This is a convenient length for manual handling. The bars are generally provided throughout the entire vertical extent of the wall. Most often, several vertical lengths are joined together to accomplish this goal. The vertical reinforcing rods are introduced into the hollow cores prior to introducing the grout. The number of vertical reinforcing rods along with their locations are dictated by building codes and design specifications. For instance, some applications may require that each core contain a vertical reinforcing rod. Other application may require vertical reinforcing rods at spaced intervals, for example, at every fifth core.
In practice, the length of the individual reinforcing rods is typically less than the height of the core to be reinforced. Hence, it is necessary to splice or tie several vertical reinforcing rods together such that a continuous reinforcing rod structure extends vertically through the entire height of the core. Building codes and design specifications dictate the necessary overlap between the rods comprising the vertical spliced joint. Such spliced joints are sometimes achieved by using wire to tie the vertical reinforcing rods together at the splice joint.
In a reinforced hollow block wall, horizontal reinforcing rods may also be used. These rods run perpendicularly to the vertical reinforcing rods. In practice, these horizontal reinforcing rods are typically placed in a "bond beam" course. In the horizontal direction of a hollow block wall, hollow cores are generally not present. Hence, the installation of horizontal rods is more difficult than the installation of vertical reinforcing rods. To facilitate installation of horizontal reinforcing rods, the outside webs and central web of the hollow blocks may be notched, or cut.
The vertical reinforcing rods are optimally tied, welded or otherwise connected to the horizontal rod to increase the strength of the hollow block wall and create a bar grid pattern. The vertical reinforcing rods must be accurately positioned to permit this connection, and prior art construction techniques are not believed to readily accommodate this connection.
Hollow block walls are further reinforced by the introduction of webbing, mesh or other planar reinforcing members within the horizontal mortar joints present between successive courses of block. During the construction of a hollow block wall, horizontal stiffeners may be placed or embedded in the mortar joint, further enhancing wall strength.
For structural purposes, it is important to precisely locate vertical reinforcing rods relative to the cells of the hollow blocks. Some applications may require vertical rods be positioned centrally within the cells, whereas other applications may require other lateral positions be maintained. Vertical positioning of the rods is critical for maintaining overlap in joints, positioning with bond beams and other related purposes.
Current methods of constructing a reinforced block wall are believed to be similarly unsophisticated. Typically, a foundation is first provided. This is most often a poured concrete structure. The foundation has a flat, upper surface. After appropriate measurements are made, the foundation may be drilled at regular intervals to receive vertical reinforcing rods. The vertical rods, however, are generally not installed at this time. An initial course of hollow blocks is then laid on the flat, upper surface of the foundation. The blocks are laid in horizontal end-to-end fashion, and are joined to one another and to the foundation by the use of a cementitious binder material, typically mortar. The mortar is applied to the outer edges, or "ears" of the hollow blocks using standard masonry techniques. Mortar is then applied to the upper surface of the first course of blocks using well-known techniques and successive courses of blocks are laid atop this first course. The upper courses are overlapped to create the so-called "half-lap" joint.
After approximately two courses of block have been laid, vertical reinforcing rods are often lowered into the cores of the hollow blocks such that the lower ends of the reinforcing rods engage the pre-drilled holes in the foundation, and the rods are epoxied into place. The length of these vertical rods is approximately equal to the height of the courses laid at this time.
At this point, construction may then generally take one of two methods. In the first method of construction, additional lengths of reinforcing rod are tied or welded to the lower lengths of reinforcing rod.
Once the second set of vertical reinforcing rods has been installed, masons must lift the hollow blocks over the vertical reinforcing rods, and then lower the blocks down, such that the hollow blocks are "threaded" onto the reinforcing rods. This is a difficult and time consuming process. Great physical effort must be expended by the mason in lifting and lowering the blocks over the vertical rods. In addition, applying mortar to the blocks also presents problems. If the mortar is applied prior to the lifting and lowering process, the mortar is often inadvertently brushed off, or drops off due to the effects of gravity. Applying the mortar to the block after it has been lowered over the rods is also difficult because the block may not be easily maneuvered once it is installed over the rods. In addition, the vertical rods obstruct access to the various surfaces of the hollow block, impeding application of mortar.
Once the blocks have been laid to a height corresponding to the height of the vertically extending rods, additional vertical rods are connected to the lower rods which again extend above the height of the partially constructed wall. The process described above is repeated, and additional courses are laid until the height of the wall reaches the height of the vertically extending rods. This method is continued until the hollow block wall is constructed to a desired height. In this manner, a hollow block wall is constructed which contains continuous vertical reinforcement through the cores of the blocks. Horizontal bond beams may also be provided near the top of the wall, but this further complicate construction. Grout is then pumped into the cores, allowed to harden and the wall is complete.
The second well-known method for constructing a hollow block wall is to first construct the wall to its desired height and subsequently lower vertical reinforcing rods down into the cores. This method does not require masons to lift blocks up and over the vertical reinforcing rods and permits rapid construction of walls. At first impression, this method would appear to be the desired method for providing vertical reinforcing rods in a hollow block wall. However, for several reasons, this method has limited application.
First, building codes and design specifications almost universally require that vertical reinforcing rods run the entire height of the wall. Thus, if a single vertical rod is to be installed in a given core, sufficient headroom must exist so that the vertical rod may be positioned over the core and lowered in. In practice, the requisite overhead clearance is typically not present. Block walls are often built in multistory structures. Steel decks separate the floors and are constructed prior to installation of the hollow block walls. These decks thus limit the amount of overhead room. In addition, block walls are often constructed between pre-existing floors and ceilings. These ceilings limit overhead clearance and make it impossible to lower in vertical rods after the wall has been constructed. This is because once the wall is constructed to ceiling height, no overhead clearance is available to lower in the vertical rods.
Other factors make it infeasible or impractical to lower in vertical rods after the wall is constructed. In many instances, pipes, ductwork, electrical conduit and other obstructions intersect the block wall at the precise location where a vertical reinforcing rod is to be positioned. This leads to the situation where vertical rods must be cut to allow for installation of such ductwork. In other situations, ductwork is already installed, and prevents the lowering of the vertical reinforcing rods. In yet other situations, horizontal meshing has been introduced and embedded in the horizontal joints of the block wall, further impeding installation of the vertical rod.
As a result, the most widely used method in constructing vertically reinforced block walls is the first method described. This entails the time consuming task of installing the vertical rods, and then raising and lowering the blocks over the rods to complete the construction of the wall.
The current holder technology, such as seen in U.S. Pat. No. 4,107,895 is not believed to permit the vertical adjustment and positioning of vertical reinforcing rods. Such reinforcing rod positioners span the open cells of the hollow blocks, and typically are designed to facilitate only horizontal positioning of the reinforcing rod within the hollow block cell.
Accordingly, it would be useful to develop a reinforcing rod holder which would make vertical positioning of the reinforcing bars a less onerous task. Further, it is desirable to provide an invention which would permit the construction of vertically reinforced, hollow block walls in areas with limited overhead clearance without the need to raise and lower blocks over preinstalled vertical rods.
It is believed that none of the prior art devices permits a block wall to be constructed while simultaneously raising the reinforcing rod through the hollow core of the block wall to correspond to the height of the block wall under construction.